/Engine/Source/Developer/BSPUtils/Public/BSPOps.h
Represents a sparse granular 3D grid into which points are added for quick (~O(1)) lookup. The 3D space is divided into a grid with a given granularity. Points are considered to have a given radius (threshold) and are added to the grid cube they fall in, and to up to seven neighbours if they overlap.
class FBspPointsGrid